It is increasingly important that a physician or surgeon delivering substances, such as an imaging or treatment agent or drug, is able to safely, efficiently and accurately occlude a blood vessel at a region of interest to visualize or treat a desired target tissue for effective delivery of the substance. Moreover, it is also important that the physician or surgeon is able to efficiently and accurately remove the occlusion of the blood vessel (allow perfusion of the target tissue) after the desired time interval to avoid damage to the desired target tissue, such as by lack of oxygen. This is particularly true when the desired concentration and/or resident time of the substance required at the target site cannot be safely and/or effectively achieved by introduction of the substance to a location remote from the target site. Moreover, the physician may only want to treat the diseased portion of an organ or tissue to avoid treating any healthy portion. In a similar manner, a physician or surgeon may use vessel occlusion to selectively deliver an imaging agent or transparent flushing fluid to the inner diameter (ID) of a vessel. For example, an imaging agent may be injected with vessel occlusion or partial occlusion to more easily/selectively visualize the vessel “roadmap”, to more easily visualize/measure the tissues that may be subsequently treated, to label a map of such tissues or to observe/measure the tissues' perfusion and/or clearance/wash out characteristics. A transparent flushing fluid may be injected with vessel occlusion, for example, to improve optical coherence tomography (OCT) imaging or the light application of a photodynamic therapy.
For example, to achieve localized treatment of tissue, such as tissue in a heart, physicians and surgeons can use catheters with occlusion devices, such as balloons. Specifically, blood vessels, such as arteries and veins, can be temporarily occluded during treatment by inflating a balloon at a region of interest of the vessel to block blood flow and thus avoid or retard the washing away of the imaging or treatment agent or drug by the flowing blood. After treatment, the region of interest may then be perfused (blood allowed to flow) by deflating the balloon to unblock the vessel.
In some cases, cardiovascular guide catheters are generally percutaneous devices used to advance through a vasculature of a patient proximal to a region of interest and are devices through which another catheter or device may be inserted. Similarly, guidewires may be advanced through a guide catheter and further into the vasculature, across a vascular region of interest. Infusion or delivery catheters are generally catheters used to deliver or infuse a treatment and/or imaging agent to a region of interest in a vasculature of a patient and typically may be engaged with a guidewire and inserted through another catheter (e.g., a guide catheter) and advanced into the vasculature to the desired region of interest. Moreover, occlusion devices, such as occlusion balloons, may be attached to a guide catheter, a guidewire or an infusion catheter to occlude and then perfuse (remove the occlusion and allow blood flow through) a region of interest in a vasculature. Additionally, a guide catheter or infusion catheter may be used to deliver or infuse a treatment and/or an imaging agent to a region of interest in a vasculature of a patient proximal or distal to the occlusion device before, during or after an occlusion.
In addition, an inflation-deflation device may push fluid into and retract fluid from the interior or cavity of the occlusion device or balloon via a catheter to inflate and deflate the occlusion device or balloon (e.g., such as using a lumen or tube in the catheter to communicate a fluid between the inflation device and the inner chamber of a balloon). To help control the outer diameter of a balloon and for safety reasons, the catheter and balloon may be aspirated (remove air and replace it with a fluid) prior to inflating the balloon with fluid to occlude the blood vessel. The fluid most often used to aspirate the catheter and balloon and inflate the occlusion balloon is contrast or a mixture of contrast and saline. Contrast is an imaging agent that allows the balloon to be imaged by an imaging modality such as fluoroscopy, MRI or ultrasound. Occlusion of the vessel is generally confirmed by injecting contrast into the guide catheter and observing by fluoroscopy that none of this contrast flows past the inflated balloon and/or by observing a pressure change due to the occlusion (i.e. the pressure of the blood may be monitored via a lumen of the catheter). Balloons may be made of a variety of materials and their inflation controlled to create non-compliant, compliant and elastic balloons. A non-compliant balloon, like those commonly used on balloon dilation catheters, may be used at moderate or low pressures (compared to dilation pressures) to occlude a vessel safely over a very small range of vessel diameters. However, conventional means to determine a vessel's inner diameter (usually fluoroscopy) are not highly accurate, especially in eccentric vessels/vessels with atheroma. If the device balloon size chosen is too small, then adequate vessel occlusion may not be obtained. If the device balloon size chosen is too large, then the vessel wall may be unnecessarily damaged by over expansion in a manner that may result in a dissection and/or a subsequent vessel stenosis or restenosis. Generally, a compliant, small volume balloon may be used to allow for more rapid balloon inflations and deflations and for more adjustable balloon diameters to allow vessel occlusion over a wider range of vessel diameters at lower balloon pressures. Generally, an elastic, small volume balloon allows for far more adjustable balloon diameters to allow vessel occlusion over a much wider range of vessel diameters at even lower balloon pressures. The difference between a compliant balloon and an elastic balloon is that a compliant balloon will not return to very nearly its original uninflated size (OD) or shape after inflation to its maximum designed size (OD), whereas an elastic balloon will return to its original uninflated size (OD) and shape after inflation to its maximum designed size. Often a compliant balloon will have an initial, pre-insertion, or nominal ID that is larger than the outer diameter (OD) of the catheter/device that it is mounted on and, thus, the compliant balloon will be folded to hug the catheter/device shaft during insertion into a vessel. Often the ID of an elastic balloon will closely fit to the OD of the catheter/device that it is mounted on and not require folding. Lower inflation pressures are desired, as less pressure is then available to damage/expand the vessel wall, if the balloon is over-sized due to an accidental misadjustment, an incorrect vessel size determination or other reasons. As a limit, the inflation pressure applied to or present in an occlusion balloon may equal or exceed the blood pressure of the vessel to keep the balloon inflated and occluding that vessel. Small volume balloons are desired because of their more rapid inflation and deflation times at low pressures. A wide range of balloon diameter adjustment is desired, as fewer devices may be stocked to cover a particular vessel size range (vessel sizes vary in the anatomy and across the population) and the degree of vessel diameter determination accuracy required to choose a device that will safely occlude the vessel is reduced. In some cases, what is desired is inflation/deflation, aspiration, and occlusion balloon devices and procedures that allow for repeated occlusion and perfusion of a blood vessel with a low risk of damaging/expanding the vessel wall. For instance, there is a need for an occlusion balloon, such as an elastic small volume low pressure balloon, that will expand to predictable repeatable outer diameters in response to being inflated and deflated with predictable repeatable amounts of fluid that can be provided by an inflation/deflation device (after successful aspiration).